1. Field of the Invention
The present general inventive concept relates to an inkjet print head, and more particularly, to an inkjet print head performing a mechanism to eject droplets of ink based on a thermal driving type.
2. Description of the Related Art
An inkjet print head is a device for ejecting droplets of ink supplied from an ink cartridge toward a desired position on a printing medium and forming an image such as a character or a picture. The inkjet print head is generally divided into two types, a thermal driving type and a piezoelectric driving type, according to a mechanism ejecting the ink droplets. The thermal driving type inkjet print head makes use of a heater and generates bubbles from the ink to then eject the ink droplets by expansion force of the bubbles. The piezoelectric driving type inkjet print head makes use of a piezoelectric material and ejects the ink droplets by means of pressure which is caused by deformation of the piezoelectric material which in turn is applied to the ink.
The following description will be made in detail regarding the ink droplet ejecting mechanism in the thermal driving type inkjet print head as described above. When a pulse current flows into a heater formed of a resistance type heating element, heat is generated from the heater, and then the ink adjacent to the heater is instantly heated. Thus, the ink is boiled to generate bubbles, and the generated bubbles are inflated to apply pressure to the ink contained in an ink chamber. Thereby, the ink is ejected in a droplet form out of the ink chamber through neighboring ink nozzles. Then, as the bubbles contract within the ink chamber, the droplets begin to be separated from the nozzles. New ink is refilled into the ink chamber, and then the foregoing process of ejecting the ink in the droplet form is repeated.
The thermal driving type inkjet print head may be subdivided into two types, a coupled type and an integrated type, according to a method of forming a chamber layer and a nozzle layer. According to a method of fabricating the integrated type inkjet print head, a plurality of thin layers and circuits are formed on a semiconductor substrate by a semiconductor process, for example a photoresist process, and then the chamber and nozzle layers are integrally formed.
Meanwhile, contaminants or dust particles existing in the ink are responsible for lowering performance of the inkjet print head. In other words, when the contaminants occlude an ink channel, the ink fails to be smoothly supplied into the ink chamber. These contaminants may be introduced in the process of packaging the inkjet print head as well as the ink cartridge. In particular, fine contaminants may still exist in the ink even after the ink passes through a filter of the cartridge. For this reason, in order to improve the performance of the inkjet print head, it is required to filter the contaminants existing in the ink to prevent the ink channel from being occluded by the contaminants.
FIG. 1A is a cross-sectional view showing an example of a conventional inkjet print head 100 capable of filtering contaminants, particularly disclosed in U.S. Pat. No. 6,582,064.
Referring to FIG. 1A, the ink is supplied from an ink via 110 of a chamber layer a through an ink channel 130 to a heater 150 in an ink chamber 120. A nozzle layer b is provided on an upper surface of the chamber layer a. A filter 140 is provided at an entry of the ink channel 130, thereby preventing contaminants 160 from entering the heater 150.
However, the inkjet print head 100 disclosed in U.S. Pat. No. 6,582,064 has a limitation of filtering of the contaminants 160, for example taking a window or rod shape, contained in the ink, because openings 141 defined by the filter 140 are arranged in parallel with respect to an ink introducing path.
FIG. 1B is a plan view showing another example of a conventional inkjet print head 200 capable of filtering contaminants, in which a nozzle layer is separated from a chamber layer.
Referring to FIG. 1B, an ink channel 230 is provided with a plurality of restrictors 260 and filters 240, wherein each filter 240 takes a pillar form. Each restrictor 260 not only applies a proper impedance to the ink supplied from an ink via 210 to a plurality of ink chambers 220, but also inhibits bubbles generated in each ink chamber 220 from expanding toward the ink channel 230, thereby facilitating the refilling of new ink. The filters 240 are formed with a row of insular elements, thereby filtering various kinds of contaminants and simultaneously preventing heaters 250 or nozzles from being clogged.
The restrictors 260 and the filters 240 may be formed either through a semiconductor process such as a photoresist process or a micro electro mechanical system (MEMS) process such as a mold process, a fill-up process or so forth. These restrictors 260 and filters 240 are arranged to alternate with each other, so that the contaminants or dust particles of an elongated spear or bar type are prevented from being introduced into the ink chambers 220.
However, the inkjet print head 200 shown in FIG. 1B is provided with the filters 240 between the heaters 250 and the ink via 210, thus having limitations to enhance a printing speed. Specifically, in order to enhance the printing speed by shortening a refill period of the ink, a distance SH between each center of the heaters 250 and the ink via 210, or a supply port-heater distance, must be as short as possible. Hence, provision of the filters 240 between the heaters 250 and the ink via 210 as in the inkjet print head 200 shown in FIG. 1B experiences limitations to enhance the printing speed.
In addition, the inkjet print head 200 shown in FIG. 1B has a problem in that, because the restrictors 260 are provided to the nozzles respectively, at least one of inlets of the nozzles may be blocked by the contaminants which may be generated during the process of packaging the head and cartridge, and thus the ink can not be ejected through the blocked nozzle.